FIG. 1 is a schematic sectional view showing the structure of a conventional optical path converting type optical coupling element 1 (e.g., JP-A-9-281302). In this optical path converting type optical coupling element 1, plural micro lenses 3 are arranged on the front face (or lower face) of a glass substrate 2. An inclining face 4 is formed in the upper portion of the rear face of the glass substrate 2, and the lower face 5 of the glass substrate 2 is formed so as to become a horizontal face.
FIG. 1 also shows a using state of this optical path converting type optical coupling element 1. Each of plural optical fibers 6 is opposed to each micro lens 3 arranged on the front face of the optical path converting type optical coupling element 1. A light receiving element 8 mounted onto a substrate 7 is arranged at a converging point of light L emitted from each optical fiber 6 and totally reflected on the inclining face 4. Accordingly, if such an optical path converting type optical coupling element 1 is used, the light L emitted from the optical fiber 6 is converged by the micro lens 3 and is introduced into the glass substrate 2 and is totally reflected on the inclining face 4. Thus, the direction of the light is converted downward, and the light L emitted from the lower face 5 of the optical path converting type optical coupling element 1 is converged on a light receiving face of the light receiving element 8.
In such an optical path converting type optical coupling element 1, the micro lens 3 is arranged on only one of the front face and the lower face of the glass substrate 2. Therefore, no bidirectional coupling can be performed between the optical fiber and the light receiving element or a light emitting element. Namely, when the optical fiber 6 is opposed to the front face of the optical path converting type optical coupling element 1 and the light receiving element 8 is arranged on the lower face of the optical path converting type optical coupling element 1, it is necessary to arrange the micro lens 3 on the front face of the optical path converting type optical coupling element 1 as shown in FIG. 1. Further, when the optical fiber is opposed to the front face of the optical path converting type optical coupling element 1 and the light emitting element is arranged on the lower face of the optical path converting type optical coupling element 1, it is necessary to arrange the micro lens on the lower face of the optical path converting type optical coupling element 1.
Accordingly, it is conventionally necessary to manufacture the optical path converting type optical coupling elements 1 of different structures when the optical path converting type optical coupling element 1 is used between the optical fiber and the light receiving element, and when the optical path converting type optical coupling element 1 is used between the optical fiber and the light emitting element. Further, no optical path converting type optical coupling element 1 can be used when the bidirectional coupling is performed between the optical fibers.
The inventors of the present invention have tried a method in which the position of an end face of the optical fiber is shifted until a focal position of the micro lens 3 and a lens substrate arranging plural micro lenses (micro lens array) therein is attached onto the lower face 5 of the optical path converting type optical coupling element 1 so as to bidirectionally use the optical path converting type optical coupling element 1 as shown in FIG. 1.
However, if the lens substrate having the plural micro lenses is intended to be attached onto the lower face 5 of the optical path converting type optical coupling element 1, it is necessary to make an optical axis adjustment (core adjusting work) of the micro lens 3 of the front face of the glass substrate 2 and the micro lens arranged in the micro lens substrate. Therefore, it becomes difficult to assembly the optical path converting type optical coupling element 1. Further, since the optical fiber must be arranged in a position far from an original set position, it also becomes difficult to make the optical axis adjustment of the optical fibers. Further, since the number of parts is increased, it takes time and labor to assemble the optical path converting type optical coupling element, and its cost is raised.
Patent literature 1: JP-A-9-281302